Laminated assembly



Jan. 22, 1952 F. GRAY LAMINATED ASSEMBLY Filed June 19, 1947 INVENTORFRANK GRAY ATTORNEY Patented Jan. 22, 1952 LAMINATED ASSEMBLYFranlrGray, London, England, assignor to International Standard ElectricCorporation, New York, N. Y., a corporation of Delaware Application June19, 1947, Serial n m'zsass 'In Great Britain May 17; 1946 Saa i, PublicLaw 690, August a, 1946 t Patent expires May 17, 1966 This inventionrelates to equipment orparts thereof built up of layers o1 material in.which the overall height of a laminated assembly has i cl i (or.Hag-298) to be within predetermined manufacturing limits.

Many equipments of this type are met with in the light electrical field,for instance. in telecommunication equipment. p

It is convenient to state the problem to which the invention relatesandindicate its solution in relation to a particular type of equipment;

One such piece of equipment is the bank of an electromagnetic switchsuch as is used in auto matic telephone systems. Such a bank comprisesstraight or arcuate rows of contacts insulated and spaced from oneanother. Such switches comprise movable contacts or wipers adapted tomove relative to the bank, each Wiper during movement contacting in turnwith each contact in associated row of contacts in the bank.

It is necessary for eiiicient operation that the contact rows in a bankshall be accurately spaced so that the associated wipers shall contactits associated contacts with the correct pressure dur" ing movement.

It is clear that commercial variations in the thickness of material usedfor making the contacts, and separators may lead to undue variations inthe spacing of contact rows: in fact, the difficulties are so great thatit has heretofore been necessary to grade and select certain members ofsuch an assembly in order to ensure that the spacing of contact rows iswithin allowable limits.

The difliculties arise due to the fact that the cumulative manufacturingtolerances allowable on the thickness dimension of the various materialsfrom which the separators, contacts, insulators, etc. are made, aresuch, that in the worst Max condition the banks require excessivepressure to compress them within the required limits, whilst in theextreme Min condition, the banks are undersize if compressedsufliciently to grip the terminals so that they will resist the poundagetest.

It has now been found that this difiiculty can be simply and cheaplyovercome in a manner which allows commercial material to be used withoutspecial grading according to thickness.

The method used consists in employing for an element or elements of apile-up metal of a com-= mercial thickness near the minimum thicknessrequired, in the case of switch banks for aluminum spacers, and formingribs or other deformations, e. g. domes therein of such height that theribs can be deformed to the required thickness by 2 the pressure appliedin assembly. Any material having suflicient plasticity and strength tobe suitable for the. formation of ribs and capable of crushing underpressure to a desired extent and not more could be used for thispurpose. metals such as aluminium, brass or copper are suitablematerials.

The method can also be' applied for instance to contact spring pile-upsfor telephone-type relays and to telephone jack strips but of course isapplicable to the manufacture of any light electri'cal equipment inwhich the problem arises.

The invention will be described with reference to certain embodimentsillustrated in the accompanying drawings in which:

Figs. 1 and 2 show in plan and end elevation a ribbed aluminium spacerfor a switch bank forming part of an up-and-around telephone typeselector switch.

Fig. 3 shows an end view of a typical contact bank embodying the presentinvention.

Fig. 4 is a cross-sectional elevation of a jack strip embodying theinvention.

A switch bank of the type in which the spacer shown in Figs. 1 and 2 maybe used is shown in Fig. 3.

Each layer of contact terminals l is placed between laminations 2 ofprepared cambric and synthetic resin bonded paper sheet for purposes ofinsulation. Metal separators 3 are placed between adjacent layers andthe whole pile-up is then clamped between steel end plates 4, compressedto the required overall sizes and securely bolted up by means of thebolts 5. It should be mentioned that after tightening is complete, theterminals must resist a lateral pressure of 4 lbs. which is momentarilyapplied to the extreme tip (outer) of each terminal for test purposes.

The aluminium separators or spacers 3 as shown in Figs. 1 and 2 havefixing holes 6 provided between arcuate ribs 1. The thickness of thematerial according to commercial ratings is near the minimum limit laiddown for the spacers. The height of the ribs is carefully chosen toensure that when the assembly is compressed the ribbed spacers give waysufficiently to enable the correct overall thickness of the bank to berealized in spite of the normal commercial variations in the thicknessof the component parts, whilst at the same time, the terminals are heldsufficiently tightly to resist the required test pressure.

By means of this provision, it is possible to manufacture the banksusing components made from materials supplied to reasonable commercialtolerances on thickness and by virtue of Soft this, the necessity forexpensive operations to grind or otherwise regulate the materials toclose dimensional tolerances on thickness has been avoided. In fact itis possible to buy to wider commercial limits than before, e. g. 1.002inch as against 10005 inch in a thickness of the order of inches andstill avoid grading and selection of material.

The preferred overall maximum height of the space at the ribs is withaluminium thick to the above limits.

Fig. 4 shows the application of the invention to jack strips in whichthe problem arises due to commercial variations in the thickness ofsheet ebonite. Each jack assembly comprises a sleeve 8 of brass and tipand ring spring contact pairs 9 and I0 with interleaved spacers H.

The root numeral 12 of the sleeve 8 is corrugated or ribbed as shown at13 for the purpose specified. Each individual jack pile up is pressedtogether and insertedjn a slot or milled groove I4 in an ebonite block15.

The ribs not only. allow the pile-ups to be compressed to therequiredheight for insertion in its groove but also makes the positioninof the pile-up in the groove more secure.

The invention can be applied to equipment comprising one or morelaminated assemblies or pile-ups: an up-and-around switch of courseusually comprises three contact banks.

' What is claimed is:

A contact bank comprising a series of rows of contact elements, having aplurality of con- 4 tact elements in each row, a pair of strips ofinsulating material, one on each side of each row. a. plurality ofmetallic spacing elements each corrugated throughout its length, onespacing member inserted between each pair of rows of contacts with oneof the strips of insulating material on each side thereof, and means forclamping the elements together into a unit of a desired dimension byflattening the corrugations of each spacing element as the clampingmeans is tightened.

FRANK GRAY.

REFERENCE S CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,049,940 Streichert Jan. 7, 19131,715,143 Nixon May 28, 1929 2,087,311 Wensley July 20, 1937 2,087,330Pagenkopf July 20, 1937 2,120,980 Johnston June 21, 1938 2,154,338, KnosApr. 11, 1939 2,277,443 Livingston Mar. 24, 1942 2,334,897 Baker Nov.23, 1943 2,395,300 Slauson Feb. 19, 1946 FOREIGN PATENTS Number CountryDate 439,500 Great Britain Dec. 9, 1935

